Linda Lye, an American Civil Liberties Union lawyer, outside the San Francisco Federal Building. Five men have filed a lawsuit that challenges the Suspicious Activity Reporting database.CreditAlex Washburn/Associated Press

WASHINGTON — Intent on not overlooking clues about any terrorist plots after the attacks of Sept. 11, 2001, the government spread a now-familiar slogan: “If you see something, say something.” Less visibly, it built a national database to better harness reports of suspicious activity in the hunt for terrorists.

On Thursday, five California men opened a legal front over the recurring tensions between collective security measures and individual rights by filing a lawsuit that challenges the Suspicious Activity Reporting database. They contend that it is too easy for people engaged in innocuous activities to be put into the database and scrutinized as if they were a threat.

The plaintiffs include two white photographers who were confronted by security guards at a natural gas tank and by the police at a refinery; an Egyptian-American who tried to buy a large number of computers at a Best Buy store; a Pakistani-American who was looking around in a train station with his mother, who wore a Muslim head scarf; and a white Muslim convert who was looking at a flight simulator game on the Internet.

Each contends that he was added to the database for his behavior, although only two, according to previously disclosed government documents, have been able to prove it. The lawsuit argues that federal standards are too lax in allowing a security guard’s or a police officer’s report to be uploaded into the national database.

The Justice Department did not immediately respond to the lawsuit, which was filed in Federal District Court in San Francisco. The suit was organized by the American Civil Liberties Union and Asian Americans Advancing Justice-Asian Law Caucus, working with lawyers for the law firm Bingham McCutchen.

“The problem with the suspicious-activity reporting program is that it sweeps up innocent Americans who have done nothing more than engage in innocent, everyday activity, like buying laptops or playing video games,” said Linda Lye, an A.C.L.U. lawyer. “It encourages racial and religious profiling, and targets constitutionally protected activity like photography.”

Scott G. Erickson, a police officer in San Jose, Calif., argued against placing more restrictions on reports when they are uploaded. Mr. Erickson, co-writer of a policy report for the conservative Heritage Foundation that lauded the system, said the whole point was to help intelligence analysts identify patterns that offer insights into terrorism from what may appear to be useless or innocuous bits of information.

Emphasizing that he was speaking for himself and not his department, Mr. Erickson said that analysts must not “rubber-stamp” decisions to pass reports on to bigger databases, and that he understood that “no one wants to find themselves in some database of potential terrorists when they’re not.”

“But at the same time,” he said, “you have to defer to the expertise of law enforcement professionals.”

The Suspicious Activity Reporting system has created a repository for data picked up from security guards and the local police that could indicate plans for a terrorist attack. The database is used by counterterrorism analysts at the state and federal levels, including regional fusion centers, where agencies pool information to look for patterns and perform background checks.

The program is jointly run by the F.B.I. and the Department of Homeland Security and uses the F.B.I.’s e-Guardian database as a repository. It was built in stages over the past decade by the Bush and Obama administrations, propelled by a 2004 law and the Nationwide Suspicious Activity Reporting Initiative begun in 2007. The government has since put out standards and training materials regarding the system, and a 2012 White House strategy document hailed its “significant progress.”

It is rapidly growing. According to a 2013 report by the Government Accountability Office, there were 27,855 suspicious-activity reports in the national databases by October 2012, up from 3,256 in January 2010. More than 71,000 queries had been submitted as of February 2013, from 2,800 in July 2010. The system does not track arrests and convictions stemming from the program, the report said.

But the lawsuit questions whether the system has delivered real benefits, and it says the standards for the uploads are too low and were written without following certain legal procedures.

Among other things, federal rules call for submitting reports about suspicious behavior that “may be indicative” of plans for a terrorist attack or some “other illicit intention.” It says that rule clashes with a Justice Department regulation from 1978 that prohibits the dissemination of “criminal intelligence information” unless a higher standard of “reasonable suspicion” has been met.

The lawsuit also contends that the system can lend itself to racial profiling. It points to reports involving plaintiffs like Khaled Ibrahim, an American citizen of Egyptian descent who lives in San Jose, Calif. The suit said that he worked as a purchasing agent for a computer consulting and service company and that “on several occasions” in 2011 tried to buy a large number of computers for the firm at a Best Buy store, which told him it did not sell computers in bulk.

It turned out he was reported to the police. The report made its way to a fusion center in Sacramento and was uploaded to the e-Guardian database.

Mr. Ibrahim is “deeply troubled by what may result from the collection, maintenance and dissemination in a national database of a report describing him as engaging in suspicious activity with a potential nexus to terrorism,” the lawsuit said.

A version of this article appears in print on , on Page A14 of the New York edition with the headline: Lawsuit Contends Surveillance Database Is Too Lax on Reporting Criteria. Order Reprints | Today’s Paper | Subscribe

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